Any ideas on converting this to run in MOTW?

It seems pretty simple, if you distill it down to what it is rather than the fluff around it.

When players try to investigate, they have to roll a 12+ to remember what they're investigating, or what they get out of a 7-11 is fleeting. Their characters lose memories quickly.

If it's singing, they're invisible. They cannot attack while invisible, so they could work like a ghost or something. Tracks of dirt lead toward them, but the characters can't recognize why the trails are important.

The silence means they're visible. It is important that you note when the silence starts, as that means that their minds are no longer blocked. They can see the enemy and maybe be hurt or hurt them back. They can read a bad situation right away.

My keeper did something similar, but not completely the same, where we could individually remember what we found, but not share it. At the party, a haloowen one to be specific, we started to remember that this isn't the first party, and people go missing every year.

Another idea is to start in media res, and just basically eff with the players in a way that seems like you're giving them loot pinatas, until you drop the bombshell on them.

The first thing I think of is "okay, eventually this thing is gonna eat someone important" and by that I mean where their 'loss' is going to cause a fuckup. Maybe a drawbridge operator gets ate and everyone is like "why the hell isn't the bridge going up for me to float my boat under?" Or "hey, we lost power and nobody at the company seems to know why"

So the keeper plays it like a ghost story or poltergeist tale. Weird goings on that seemingly have no explanation.

And you drop little weird hints like "you exit the building and your big black van is waiting for you" (and nobody had a van at chargen)

Then they go check things out. "Hey, isn't someone supposed to be working here?" And the townies are like "yeah sure" and the players are like "who?" And the townies are like "I...don't know?"

Then at the very end of the tale, you drop the bomb. Belongings of all the eaten individuals, and amongst them, a wallet with pictures, including the players with 1+ people they don't know, in their black van, and an insurance card for that person/van (for example).

It'd be pretty sobering to be playing with a team and realize that not only have you been fighting this thing for a while, you have been consistently losing members.